The present invention relates to a capillary electrophoresis apparatus for separating and analyzing DNA, protein, and the like.
Techniques of analyzing DNA, protein, and the like are important in the medical and biological fields including gene analysis and gene diagnosis. A DNA analyzing apparatus having high throughput is being developed recently. Those analyses are mainly performed by a gel electrophoresis. In the gel electrophoresis, a substance in a gel state is used as a separating medium of the electrophoresis, DNA labelled with fluorophore is usually prepared and the fluorescence labelled DNA sample is injected into the upper end of polyacrylamide gel formed between two glass plates (slab gel). After that, an electrical field is applied to both ends of the gel, components (fragments) of the sample DNA are allowed to migrate to the lower end, a predetermined position from the upper end is irradiated with laser light, and fluorophore is detected. The result is analyzed, and DNA base sequence is determined or polymorphism of a restriction fragment is identified. Recently, in place of the slab gel, a capillary gel obtained by polymerizing gel in a capillary is often used. Attention is paid to a capillary electrophoresis as a method which enables high speed and high separation since an electric field larger than that used in the slab gel electrophoresis can be applied. In a capillary electrophoresis apparatus, on-column measurement in which one capillary column is used, capillaries near the lower end are irradiated with laser light, and the fluorophore is detected, is usually used ("Bunseki", 1995, No. 5, pp. 342-349).
A capillary array gel electrophoresis apparatus for simultaneously analyzing a number of samples by using a plurality of capillaries in order to improve the throughput has been reported. According to a first example, on-column fluorescent measurement is performed in such a manner that a plurality of capillaries are arranged on a moving stage and the moving stage is moved, thereby sequentially irradiating the capillaries one by one with laser light ("Analytical Biochemistry", 215, pp. 163 to 170, 1993). A second example relates to a method of using a sheath flow (Japanese Patent Application Laid-Open No. 06-138037 and U.S. Pat. No. 5,529,679). In an apparatus according to the second example, the lower end of a capillary array is soaked in a buffer solution, components of the sample separated by the gel electrophoresis are eluted in the buffer solution, and fluorescent light from the sample component is detected in a part where no capillary exists.